Studies of heat transfer and chaos in a gas-fluidized bed with an opposing oscillatory flow

An innovative hybrid coal combustion technology integrates a pulsed combustor with a fluidized bed combustor. The pulsed combustor is oriented vertically with the oscillatory secondary flow exiting the tailpipe in opposition to the primary flow through the distributor. An experimental facility was designed to simulate the hydrodynamic conditions of the hybrid combustor and instrumented to measure both overall and local instantaneous heat transfer coefficients from a heated horizontal cylinder. The pulsed combustor was simulated using a resonant tailpipe and a reciprocating piston with variable amplitude and frequency capabilities.; The facility was operated with a range of particle sizes from 130 {dollar}mu{dollar}m to 715 {dollar}mu{dollar}m and a range of superficial fluidization velocities corresponding to the bubble flow regime. Measured values of heat transfer show significant effects of the secondary flow and its oscillatory amplitude and frequency. Enhancements in the overall heat transfer coefficient up to 20 percent for the 715 {dollar}mu{dollar}m particles resulted from distributing the total flow through two opposing streams. The effects of the amplitude and frequency of the oscillatory flow on particle Nusselt number were described effectively by a modified Strouhal number. The magnitude and angular distribution of local heat transfer were significantly altered by an opposing oscillatory flow with measured enhancements of more than 50 percent. Analysis of the contact dynamics reveals that the primary contribution to increased average local heat transfer coefficients is an increase in the average bubble and emulsion phase heat transfer coefficients.; Chaos analysis techniques were employed to assess and quantify the chaotic nature of local instantaneous heat transfer coefficients. Quantitative measures of entropy suggest that time-series measurements of local heat transfer display behavior that is consistent with chaos. The complexity of the heat transfer signals, as suggested by the Kolmogorov entropy, increases with primary flow rate and decreases with the introduction of the secondary flow. Several algorithms were employed to estimate the fractal dimensions which were found to be less than 5. An indirect relation between the contact dynamics and chaos measures was found to exist.